1. Field of the Invention
This invention relates to computer disk head assemblies, and more particularly to a computer disk head assembly flexure having improved mechanical characteristics.
2. Related Art
Magnetic disk drives have become an important part of the computer industry. Typical modern magnetic disk drives have a plurality of flat, circular, spaced apart disks rotating about a common spindle. Data is stored on a magnetic media formed on the surface of the disks. Data is divided into groupings called "tracks" that form concentric rings on the surface of the disks. A read/write head is positioned above each side of a disk. As the disk spins beneath a head, the head can magnetize the magnetic media in a track, thereby writing onto the track. After data is stored on a track, the read/write head can be positioned above a track, and as the disk spins, the head can read back the magnetic pattern stored on the disk track. To write on or to read from different tracks, the read/write heads merely need to be moved towards or away from the spindle.
The read/write heads typically comprise an electromagnetic core and coil mounted on a "slider"which has an air-bearing surface positioned immediately adjacent the flat surface of a disk. As the disk spins, the air following the disk applies pressure to the slider's air-bearing surface, and lifts the slider and read/write core and coil off of the surface of the disk.
The disk surfaces of disk drives are not perfectly flat, yet it is important that the air-bearing surface of the slider be substantially parallel to the disk surface. Therefore, the slider body is attached to a component called a flexure. A flexure allows the slider body to gimbal to follow fluctuations in the surface of a disk while restricting the slider's motion in undesired directions with respect to the disk. To support a flexure in the proper position, the flexure is attached to an elongated load beam which in turn is attached to an arm coupled to a carriage in the disk drive. The load beam is generally made of steel and acts as a leaf spring to bias the flexure/slider assembly towards a disk.
Over the past several years, the size of disk drives has shrunken considerably, from a 14-inch form factor down to as little as a 21/2-inch form factor at present. While the physical size of disk drives has been shrinking, the density of information storage on the disks of such disk drives has been increasing. Both the number of bits per inch (bpi) and tracks per inch (tpi) have increased significantly over the past several years. Furthermore, the speed of access of the head assembly from track to track in such disk drives has also been increasing, resulting in higher performance disk drives.
As a result of such changes, it has become increasingly important to design computer disk head assemblies to higher levels of functional precision in order to maintain the correct position of read/write heads with respect to data tracks. An important aspect of such assemblies is the flexure.
FIG. 1 shows a prior art flexure 1. The flexure 1 comprises a "tuning fork" shaped support structure 2 having a pair of outriggers 3. The attachment end 4 of the flexure 1 is attached to a load beam 10 (see FIG. 1a) of the disk drive head assembly structure.
The flexure 1 has an "I" shaped tongue portion 5 that is attached to the inner sides of the ends of the outriggers 3 by ramps 6 such that the tongue 5 is spaced apart therefrom by the height of the ramps 6. The ramps serve to separate the outriggers 3 from the slider that will be attached to the tongue 5.
A raised, rounded dimple 7 is provided in the tongue 5 such that when the flexure 1 is attached to a load beam 10, the apex of the dimple 7 rests against the load beam 10. This provides a pivot or gimbal point around which a slider, when mounted to the tongue 5 of the flexure 1, can pitch and roll with respect to the longitudinal and transverse axes, respectively, of the flexure 1. This permits the flexure --and thus the read/write head on the slider attached to the flexure --to follow fluctuations in the surface of a disk while restricting the slider's motion in undesired directions with respect to the disk. Prior art flexures of the type shown in FIGS. 1 and 1a are typically used with a radial-type actuator, which moves the head assembly towards and away from the disk spindle along a radius of the disk. When a prior art type flexure is used with a radial-type actuator, the longitudinal axis of the slider is perpendicular to the longitudinal axis of the flexure structure 1. The outriggers 3 of the flexure structure 1 permit the slider to follow the surface of an adjacent magnetic disk such that the spacing between the read/write head on the slider and the disk is maintained at an approximate constant distance.
In many present-day disk drive designs, rotary-type actuators are used instead of radial actuators. A rotary actuator moves the head assembly towards and away from the disk spindle along an arcuate path, much like the path of a pivoting tonearm on a record player.
A major problem in using prior art flexures of the type shown in FIG. 1 in a rotary type actuator is that the relationship of the slider (and hence read/write head) to the flexure is changed by 90.degree. . That is, in radial actuators, the longitudinal axis of the slider is perpendicular to the longitudinal axis of the flexure 1. In a rotary actuator, the longitudinal axis of the rotary actuator is tangential to the disks, rather than perpendicular. Thus, the slider must be positioned such that its longitudinal axis is parallel with the longitudinal axis of the flexure 1. However, since a rotary actuator moves the slider/head assembly in a arcuate path in order to move from track to track, a problem arises that did not exist with radial actuators. As the rotary actuator moves a head from side to side, a yaw motion is imparted to the slider/head assembly that is not adequately countered by the outriggers 3 of prior art flexures. The position of the ramps 6 of the prior art flexure 1 do not provide adequate stiffness against such yawing.
Yaw of a read/write head flexure is undesirable, because a head may have difficulty settling on track or remaining on track after a seek operation, thereby impairing reading or writing of data.
It is therefore desirable to provide a flexure that is designed to pitch and roll with respect to the direction of rotation of a disk while limiting yaw.
Another problem in using the prior art flexures in a rotary actuator is that the prior art flexure is not adequately compliant in the roll direction, thus interfering with the roll compliance of the slider air bearing.